Slender, usually simple, 2-5 dm, with 1 or 2(3) terminal and subterminal umbels, normally with 3 lf-bearing nodes, the lower and upper each with a pair of small lvs, the middle with a whorl of 4 much larger ones, or the lvs rarely all opposite in 4 pairs; lvs thin, lanceolate or lance-ovate, the larger 6-12 cm, acuminate, cuneate to a conspicuous petiole; peduncles 1-4 cm; cor pink to white; its lobes 4.5-6 mm; hoods 4-5 mm, much exceeding the gynostegium, the lateral margins bearing a prominent, sharp, inflexed tooth near or below the middle; horn flattened, sword-shaped, falcately incurved; fr erect on erect pedicels, very slender, 8-12 cm. Dry upland woods; Vt. to Va. and in the mts. to n. Ga., w. to s. Ont., Ill., s. Io., and Okla., with a minor disjunction e. of the Mississippi R. May, June.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.